Likutei Sichos – Vol 17 p 401 ff Pirkei Avos Perek 6, first Mishna. He begins the Perek קנין תורה with he who learns Torah Lishma, which seems a bit much for the opener of such a Perek. He lists a series of gains that come along with Torah Lishma using various different forms. The Rebbe explains it all: we begin the Perek with the ultimate end: Torah Lishma, and we explain that various things come to one who learned Torah Lishma, some with no effort and some with some effort. This alleviates all the questions wonderfully.
